Cell culture and immunocytochemistry. HeLa cells were grown in
modified Eagle’s minimal essential medium (MEM) with 10%
NuSerum, and 1% penicillin/streptomycin from Life Technologies
(Grand Island, NY). HeLa cells stably expressing LDLR-GFP (HeLa-
LDLR-GFP) were grown in modified Eagle’s minimal essential medium
(MEM) with 10% NuSerum, and 500 lg/ml G418 from Sigma.
All cells were maintained at 37 C in a humidified atmosphere of
95% air, 5% CO2. For uptake experiments, the following concentrations
were used: Tf-FITC (40 lg/ml), LDL-DiI (5 lg/ml), and EGFAlexa488
(2 lg/ml). Following treatment with endocytic tracers
and PLA2 antagonists, cells were fixed and processed for immunofluorescence
as described [13], and analyzed with a Zeiss Axioscope
II equipped with a Hamamatsu Orca II digital camera and
Openlab software by Improvision, or a Perkin-Elmer UltraVIEW
spinning disc confocal microscope and software.